trace_events: add traced_value.cc/traced_value.h

Port of the V8 internal v8::tracing::TracedValue that allows
structured data to be included in the trace event. The v8 class
is not exported in the public API so we cannot use it directly.

This is a simplified and slightly modified port. This commit only
adds the class, it does not add uses of it. Those will come in
separate PRs/commits.

node.gyp

@@ -380,6 +380,7 @@
         'src/tracing/node_trace_buffer.cc',
         'src/tracing/node_trace_writer.cc',
         'src/tracing/trace_event.cc',
+        'src/tracing/traced_value.cc',
         'src/tty_wrap.cc',
         'src/udp_wrap.cc',
         'src/util.cc',
@@ -440,6 +441,7 @@
         'src/tracing/node_trace_buffer.h',
         'src/tracing/node_trace_writer.h',
         'src/tracing/trace_event.h',
+        'src/tracing/traced_value.h',
         'src/util.h',
         'src/util-inl.h',
         'deps/http_parser/http_parser.h',
@@ -953,6 +955,7 @@
         'test/cctest/test_node_postmortem_metadata.cc',
         'test/cctest/test_environment.cc',
         'test/cctest/test_platform.cc',
+        'test/cctest/test_traced_value.cc',
         'test/cctest/test_util.cc',
         'test/cctest/test_url.cc'
       ],

src/tracing/traced_value.cc

@@ -0,0 +1,191 @@
+// Copyright 2016 the V8 project authors. All rights reserved.
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file.
+
+#include "tracing/traced_value.h"
+
+#include <math.h>
+#include <sstream>
+#include <stdio.h>
+#include <string>
+
+#if defined(_STLP_VENDOR_CSTD)
+// STLPort doesn't import fpclassify into the std namespace.
+#define FPCLASSIFY_NAMESPACE
+#else
+#define FPCLASSIFY_NAMESPACE std
+#endif
+
+namespace node {
+namespace tracing {
+
+namespace {
+
+void EscapeAndAppendString(const char* value, std::string* result) {
+  *result += '"';
+  char number_buffer[10];
+  while (*value) {
+    char c = *value++;
+    switch (c) {
+      case '\t':
+        *result += "\\t";
+        break;
+      case '\n':
+        *result += "\\n";
+        break;
+      case '\"':
+        *result += "\\\"";
+        break;
+      case '\\':
+        *result += "\\\\";
+        break;
+      default:
+        if (c < '\x20') {
+          snprintf(
+              number_buffer, arraysize(number_buffer), "\\u%04X",
+              static_cast<unsigned>(static_cast<unsigned char>(c)));
+          *result += number_buffer;
+        } else {
+          *result += c;
+        }
+    }
+  }
+  *result += '"';
+}
+
+std::string DoubleToCString(double v) {
+  switch (FPCLASSIFY_NAMESPACE::fpclassify(v)) {
+    case FP_NAN: return "\"NaN\"";
+    case FP_INFINITE: return (v < 0.0 ? "\"-Infinity\"" : "\"Infinity\"");
+    case FP_ZERO: return "0";
+    default:
+      // This is a far less sophisticated version than the one used inside v8.
+      std::ostringstream stream;
+      stream.imbue(std::locale("C"));  // Ignore locale
+      stream << v;
+      return stream.str();
+  }
+}
+
+}  // namespace
+
+std::unique_ptr<TracedValue> TracedValue::Create() {
+  return std::unique_ptr<TracedValue>(new TracedValue(false));
+}
+
+std::unique_ptr<TracedValue> TracedValue::CreateArray() {
+  return std::unique_ptr<TracedValue>(new TracedValue(true));
+}
+
+TracedValue::TracedValue(bool root_is_array) :
+    first_item_(true), root_is_array_(root_is_array) {}
+
+TracedValue::~TracedValue() {}
+
+void TracedValue::SetInteger(const char* name, int value) {
+  WriteName(name);
+  data_ += std::to_string(value);
+}
+
+void TracedValue::SetDouble(const char* name, double value) {
+  WriteName(name);
+  data_ += DoubleToCString(value);
+}
+
+void TracedValue::SetBoolean(const char* name, bool value) {
+  WriteName(name);
+  data_ += value ? "true" : "false";
+}
+
+void TracedValue::SetNull(const char* name) {
+  WriteName(name);
+  data_ += "null";
+}
+
+void TracedValue::SetString(const char* name, const char* value) {
+  WriteName(name);
+  EscapeAndAppendString(value, &data_);
+}
+
+void TracedValue::BeginDictionary(const char* name) {
+  WriteName(name);
+  data_ += '{';
+  first_item_ = true;
+}
+
+void TracedValue::BeginArray(const char* name) {
+  WriteName(name);
+  data_ += '[';
+  first_item_ = true;
+}
+
+void TracedValue::AppendInteger(int value) {
+  WriteComma();
+  data_ += std::to_string(value);
+}
+
+void TracedValue::AppendDouble(double value) {
+  WriteComma();
+  data_ += DoubleToCString(value);
+}
+
+void TracedValue::AppendBoolean(bool value) {
+  WriteComma();
+  data_ += value ? "true" : "false";
+}
+
+void TracedValue::AppendNull() {
+  WriteComma();
+  data_ += "null";
+}
+
+void TracedValue::AppendString(const char* value) {
+  WriteComma();
+  EscapeAndAppendString(value, &data_);
+}
+
+void TracedValue::BeginDictionary() {
+  WriteComma();
+  data_ += '{';
+  first_item_ = true;
+}
+
+void TracedValue::BeginArray() {
+  WriteComma();
+  data_ += '[';
+  first_item_ = true;
+}
+
+void TracedValue::EndDictionary() {
+  data_ += '}';
+  first_item_ = false;
+}
+
+void TracedValue::EndArray() {
+  data_ += ']';
+  first_item_ = false;
+}
+
+void TracedValue::WriteComma() {
+  if (first_item_) {
+    first_item_ = false;
+  } else {
+    data_ += ',';
+  }
+}
+
+void TracedValue::WriteName(const char* name) {
+  WriteComma();
+  data_ += '"';
+  data_ += name;
+  data_ += "\":";
+}
+
+void TracedValue::AppendAsTraceFormat(std::string* out) const {
+  *out += root_is_array_ ? '[' : '{';
+  *out += data_;
+  *out += root_is_array_ ? ']' : '}';
+}
+
+}  // namespace tracing
+}  // namespace node

src/tracing/traced_value.h

@@ -0,0 +1,68 @@
+// Copyright 2016 the V8 project authors. All rights reserved.
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file.
+
+#ifndef SRC_TRACING_TRACED_VALUE_H_
+#define SRC_TRACING_TRACED_VALUE_H_
+
+#include "node_internals.h"
+#include "v8.h"
+
+#include <stddef.h>
+#include <memory>
+#include <string>
+
+namespace node {
+namespace tracing {
+
+class TracedValue : public v8::ConvertableToTraceFormat {
+ public:
+  ~TracedValue() override;
+
+  static std::unique_ptr<TracedValue> Create();
+  static std::unique_ptr<TracedValue> CreateArray();
+
+  void EndDictionary();
+  void EndArray();
+
+  // These methods assume that |name| is a long lived "quoted" string.
+  void SetInteger(const char* name, int value);
+  void SetDouble(const char* name, double value);
+  void SetBoolean(const char* name, bool value);
+  void SetNull(const char* name);
+  void SetString(const char* name, const char* value);
+  void SetString(const char* name, const std::string& value) {
+    SetString(name, value.c_str());
+  }
+  void BeginDictionary(const char* name);
+  void BeginArray(const char* name);
+
+  void AppendInteger(int);
+  void AppendDouble(double);
+  void AppendBoolean(bool);
+  void AppendNull();
+  void AppendString(const char*);
+  void AppendString(const std::string& value) { AppendString(value.c_str()); }
+  void BeginArray();
+  void BeginDictionary();
+
+  // ConvertableToTraceFormat implementation.
+  void AppendAsTraceFormat(std::string* out) const override;
+
+ private:
+  explicit TracedValue(bool root_is_array = false);
+
+  void WriteComma();
+  void WriteName(const char* name);
+
+  std::string data_;
+  bool first_item_;
+  bool root_is_array_;
+
+  DISALLOW_COPY_AND_ASSIGN(TracedValue);
+};
+
+}  // namespace tracing
+}  // namespace node
+
+#endif  // SRC_TRACING_TRACED_VALUE_H_

test/cctest/test_traced_value.cc

@@ -0,0 +1,63 @@
+#include "tracing/traced_value.h"
+
+#include <math.h>
+#include <stddef.h>
+#include <string.h>
+
+#include "gtest/gtest.h"
+
+using node::tracing::TracedValue;
+
+TEST(TracedValue, Object) {
+  auto traced_value = TracedValue::Create();
+  traced_value->SetString("a", "b");
+  traced_value->SetInteger("b", 1);
+  traced_value->SetDouble("c", 1.234);
+  traced_value->SetDouble("d", NAN);
+  traced_value->SetDouble("e", INFINITY);
+  traced_value->SetDouble("f", -INFINITY);
+  traced_value->SetDouble("g", 1.23e7);
+  traced_value->SetBoolean("h", false);
+  traced_value->SetBoolean("i", true);
+  traced_value->SetNull("j");
+  traced_value->BeginDictionary("k");
+  traced_value->SetString("l", "m");
+  traced_value->EndDictionary();
+
+  std::string string;
+  traced_value->AppendAsTraceFormat(&string);
+
+  static const char* check = "{\"a\":\"b\",\"b\":1,\"c\":1.234,\"d\":\"NaN\","
+                             "\"e\":\"Infinity\",\"f\":\"-Infinity\",\"g\":"
+                             "1.23e+07,\"h\":false,\"i\":true,\"j\":null,\"k\":"
+                             "{\"l\":\"m\"}}";
+
+  EXPECT_EQ(string, check);
+}
+
+TEST(TracedValue, Array) {
+  auto traced_value = TracedValue::CreateArray();
+  traced_value->AppendString("a");
+  traced_value->AppendInteger(1);
+  traced_value->AppendDouble(1.234);
+  traced_value->AppendDouble(NAN);
+  traced_value->AppendDouble(INFINITY);
+  traced_value->AppendDouble(-INFINITY);
+  traced_value->AppendDouble(1.23e7);
+  traced_value->AppendBoolean(false);
+  traced_value->AppendBoolean(true);
+  traced_value->AppendNull();
+  traced_value->BeginDictionary();
+  traced_value->BeginArray("foo");
+  traced_value->EndArray();
+  traced_value->EndDictionary();
+
+  std::string string;
+  traced_value->AppendAsTraceFormat(&string);
+
+  static const char* check = "[\"a\",1,1.234,\"NaN\",\"Infinity\","
+                             "\"-Infinity\",1.23e+07,false,true,null,"
+                             "{\"foo\":[]}]";
+
+  EXPECT_EQ(string, check);
+}